Ceramic tube with integrated resonator structure



Sept. 8, 1970 c. HOPPER, JR., ETAL 3,527,931

CERAMIC TUBE WITH INTEGRATED RESONATOR STRUCTURE 2 Sheets-Sheet 1 Filed March 8 1968 FIG.I.

R W NY \w U :RL C N SEL R R P o o mw W T 2 A V E Y r N E AE T LH C S A 7 av B Patented Sept. 8., 1970 3,527,981 CERAMIC TUBE WITH INTEGRATED RESONATOR STRUCTURE Claude Hopper, Jr., and Shelby A. Jolly, Owensboro,

Ky., assiguors to General Electric Company, a corporation of New York Filed Mar. 8, 1968, Ser. No. 711,657 Int. Cl. H01j 7/46 US. Cl. 31539 9 Claims ABSTRACT OF THE DISCLOSURE A microwave frequency ceramic tube cavity oscillator is provided comprising a ceramic vacuum tube portion including a surrounding wall structure and a ceramic cavity resonator portion which forms an integral part of the tube wall structure. The resonator comprises annular ceramic members, coated on their outside surfaces with conductive material, which members form anode and cathode resonator cavities. The ceramic material of the annular members fill a substantial portion of the cavities to an extent that the ceramic material itself acts as the dielectric. With this arrangement, the tube parts are disposed internally of the cavity resonators and are supported by the wall structure thereof including the ceramic members. Means are provided to feed back energy from the anode cavity to the cathode cavity for oscillator operation.

BACKGROUND OF THE INVENTION This invention relates to microwave frequency vacuum' tubes, and more particularly, to an integral structure comprising a ceramic electron discharge tube and a cavity resonator.

In the electronic and related industries, there is an everpresent desire to reduce the size and cost of components as much as is practically possible. However, in ef fecting such size and cost reduction, the electrical and mechanical integrity of the components must not be sacrificed. In fact, it is desirable that any changes toward size or cost reduction should actually increase the capability and the demands which have been made on the prior art structures. Hence, there is a continuous effort being made by those skilled in the art to effect such improvements.

In the art comprising microwave frequency electron discharge tubes, it is well known to provide, for example, a microwave oscillator comprising such a tube in combination with a cavity resonator. In such arrangements the tube is often detachably positioned within the resonator cavity and the resonator and the tube are electrically interconnected so as to act as a high frequency oscillation generator. The prior-art tubes and resonators which make up the final structure have been constructed independently of each other with the resulting requirement that the components must be finally assembled to produce the oscillator. Such assembly naturally adds to the cost of their production and, also, contributes to the overall size of the finished device. Furthermore, it is often necessary to take additional steps and expense to ensure that the resulting oscillator is a sturdy, shockresistant structure.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved microwave frequency electron discharge tube with an integral resonator structure which is more compact and less expensive to assemble than comparable prior art devices.

It is a further object of this invention to provide an improved microwave frequency tube having an integral resonator structure which enhances the overall sturdiness thereof.

In accordance with my invention in one form thereof, I provide a microwave frequecy tube comprising a vacuum tube portion including a surrounding wall structure and a cavity resonator integral with the wall structure and comprising solid dielectric members forming a pair of resonator cavities substantially filled by the dielectric material. The active parts of the tube are disposed within the resonator cavities and are supported by the wall structure thereof including the dielectric members. The cavity resonator and the tube are suitably interconnected electrically for oscillator operation.

DETAILED DESCRIPTION Other objects and advantages of the present invention may better be understood by reference to the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is an axial cross-sectional view of the oscillator structure of our invention;

FIG. 2 is a similar view of the tube electrode portion of the oscillator of FIG. 1 drawn to an enlarged scale; and

FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2.

Referring now to FIGS. 1 and 2, there is shown an integral tube-cavity resonator structure 1 of the present invention. Broadly considered, the structure 1 comprises a resonator portion 3 and a tube portion 5 which are structurally integrated and interconnected so as to provide a unitary electrical component. More specifically, the resonator portion 3 comprises a pair of resonator cavities, designated the anode cavity 7 and the cathode cavity 9. The cathode cavity 9 is formed with an annular ceramic member 11 of appropriate size for the desired operating frequency, with the outer surface of the ring bing metallized with a copper film 13. The metallizing is onto all the unshielded surfaces of the ceramic ring 11 to obtain a conducting film and then plating this conducting film with copper until the desired thickness is reached. It is to be understood that other methods of coating the ceramic member may also be utilized. A thickness of one to five mils is adequate for electrical performance; however, thicker coatings may be desired for operation under some environmental conditions and are contemplated by the present invention. The ceramic cathode cavity member 11 surrounds the cathode part of the tube portion 5, to be described, and is electrically coupled thereto.

The anode cavity 7 is similarly formed With an annular ceramic member 15 designed to fit around or surround the anode part of the tube portion 5, with the outer surface metallized with a conducting film .17 in the same fashion as that described for the cathode cavity member 11. As can be seen, the anode cavity 7 and the cathode cavity 9 are each substantially filled by the ceramic material of the members 15 and 11 respectively, the ceramic material serving as the principal dielectric medium for resonator operation.

The tube portion 5 may comprise tube elements or electrodes including, for example, a plane parallel array of cathode assembly 19, a grid 21, a plate or anode 23 and a hermetically sealed enclosure assembly 25 therefor. While a triode is here shown, it is to be understood that other known electrode arrangements, such as tetrodes, pentodes, or the like may be adapted for the present invention.

The cathode assembly 19, as shown more clearly in FIG. 2, comprises an electrically conductive cathode-support cylinder 27, a cathode cup 29 positioned at the top of the cathode support cylinder 27, and a heater structure 31 bonded to the underside of the cathode cup 29 within the cathode support cylinder 27, a free end of the heater 31 extending downwardly for connection with a heater contact or pin 33, (FIG. 1). As seen in FIG. 1, the cathode support cylinder 27 includes an annular flange portion 35 which is in electrical contact with a cathode terminal ring 37 which comprises a second heater con tact connectable with a suitable heater supply circuit (not shown). The upper surface of the cathode cup 29 includes a suitable annular electron-emissive coating which when heated provides a copious supply of electrons.

The grid assembly 21 of the tube portion 5, which may best be seen in FIGS. 2 and 3, comprises a grid frame 39 which may comprise two etched tungsten frames 41 and 43 which are brazed together. A control grid 45 is then fabricated by Winding a large number of turns of fine wire over this frame and then brazing the Wire to the frame at every point of contact. Obviously, other methods of grid assembly may be employed in the practice of the present invention. The grid assembly 21 is held in place by means of a grid retainer ring 47 which also serves to make electrical contact between the grid assembly 21 and a grid ring 49. A central section of the grid assembly 21 includes a circular aperture 51 for reception of a tungsten disc or probe 53 which is centrally disposed on the upper surface of the cathode cup 29, the said surface of the cup being uncoated with electron emissive material. The disc or probe 53, as will appear, transfers energy from the grid-anode cavity 7 to the grid-cathode cavity 9 in the proper phase and amplitude when the tube is used as an oscillator to ensure the establishment of sustained oscillations. This feature of the present invention will be described below.

The plate or anode 23 of the tube comprises a cupshaped metallic member disposed adjacent the grid assembly 21 and, in contact therewith, is a threaded anode contact 55 which is disposed in the hollow of the cylindrical anode 23. The contact 55 is brazed at the inner end thereof to the inside of the bottom of the cup-shaped anode 23.

The above description is for purposes of describing generally the elements of the tube 1. A feature of the present invention is concerned with the structural interrelation of the resonator portions 7 and 9 with the tube portion 5 of the oscillator 1 so as to effect a significant reduction in size and cost of assembly thereof, and this structural interrelation will now be described. At the cathode portion of the tube 1 and forming a portion of the tube envelope structure 25, there is provided a ceramic cup 57 through the bottom of which the heater contact 33 projects. The ceramic cup 57 also includes an upper support surface which cooperates with the underside of the cathode cavity member 11 to sandwich and support the conductive cathode ring 37 therebetween.

It can be seen that the outer surface of the cathode cavity member 11 includes the copper film 13 which is in direct electrical contact with the cathode ring 37. The flange portion 35 of the cathode support cylinder 27 is received in a slot formed by the cathode ring 37 and the cathode cavity member 11 to adequately support and position the cathode support cylinder 27 and place it in direct electrical contact with the cathode ring 37.

Support of the grid assembly 21 is accomplished by provision of a support surface 61 on the top of the cathode cavity member 11. The grid assembly 21 is retained in this position by means of the peripherally offset retainer ring 47 which is itself retained in position by the grid ring 49 sandwiched between the cathode cavity member 11 and the anode cavity member 15. The retainer ring 47 also serves to make electrical contact between the grid assembly 21 and the grid ring 49. The grid ring 49 is in electrical contact with a portion of a copper conducting film 13' formed over a portion of the upper surface of the cathode cavity ring 11. A grid lead 63 for external connection is provided in direct electrical contact with the conducting film 13 of the cathode cavity member 11. The conducting film 13' also cooperates to provide an RF bypass capacitor 65 for the grid to maintain the grid at the same RF potential as the conducting film. This capacitor 65 is formed by the conducting film 13, insulating material in the form of a mica ring 67 which is positioned on top of the top surface of the cathode cavity member 11, and a copper ring 69 which surrounds the cathode cavity ring 11 and provides electrical connection from the conducting film 17 of the anode cavity member 15 to the conducting film 13 of the cathode cavity member 11. There is, it will be noted, a break or discontinuity in the conducting film 13' starting at point 71 so that there is no direct current path to the grid from the conductive coating 13.

The anode 23 extends through a center hole in the anode cavity member 15 and is insulated from the metallized surface 17 thereof. The anode 23 is terminated for RF at the surface 17 through a bypass capacitor 73 formed, as shown, as a plurality of alternately stacked mica discs 75 and copper plates 77 and 77, the plates 77 being interconnected at their outer edges as by soldering as at 78. An additional annular ceramic spacer 79 is disposed on top of the anode bypass capacitor 73 and operates as a heat sink and as a retaining member in the envelope structure 25. The size of this spacer 79 is determined by the heat dissipating capability desired for the anode cavity. A retainer nut 81 is threadedly abutted onto the plate contact 55 to complete the mechanical assembly of the structure, the compression of the spacer 79 with the capacitor 73 serving also to increase the heat conducting capability of the disc. An ultra-high-frequency pickup loop 83 is mounted in a slot 85 of the anode cavity member 15 and is provided with an output connector 87 which is, in turn, soldered to the metallized surface 17 of the anode cavity member 15. The dimensions of the anode cavity 7 deter' mines the operating frequency of the oscillator 1.

The grid seal ring 49 comprises an active metal, such as titanium, which forms a vacuum-tight seal with the anode cavity member 15 and the cathode cavity member 11. Such a seal may be formed by a variety of techniques, such as the use of nickel bonding shims between opposing ceramic-to-metal surfaces, as are well known in the art. The cathode ring 37 also comprises an active metal which forms a vacuum-tight seal with the ceramic cup 57 and the cathode cavity member 11 by the aforementioned conventional techniques.

Inasmuch as the envelopestructure 25 of the tube portion 5, as above described, includes the lower ceramic cup 57, the cathode ring 37, the cathode cavity member 11, the grid bypass capacitor 65, the anode cavity member 15, the anode bypass capacitor 73, and the heat sink disc 79, all of which are retained as an integral rugged and shock resistant unit, the unit can be assembled in one assembling operation without the necessity of preassembly of either of the component parts. And, this can be accomplished with a substantial reduction in overall size as well as the cost savings which are effected.

The resonator cavities provide tuned circuits for tuning to the desired high frequency. As has been stated, the dimensions of the cavities and the size of the cavity rings determine the frequency at which the system is tuned, the cavity 7 serving to tune the anode-grid circuit and the cavity 9 serving to tune the grid-cathode circuit. The tube may be adapted to perform as an amplifier, if desired. In the preferred form of the invention, however, as herein described, the tube 1 is adapted for use as an oscillator. In order to provide sustained oscillation, it is necessary to provide a feedback path for energy from the output to the input circuit. This, as above noted, is provided by the tungsten disc 53 which is attached to or integrally formed with the center portion of the cathode and which comprises a generally inverted cup-iike member having a large annular base. The cup portion of the tungsten disc is disposed in the aperture 51 of the grid 21. The tungsten disc 53 transfers energy from the anode cavity 7 to the cathode cavity 9 in the proper phase and amplitude to produce the desired oscillation.

There is thus described a novel ceramic tube cavity resonator assembly comprising a resonator portion and a vacuum tube portion which are structurally interrelated so as to provide an arrangement which affects a significant reduction in cost and size over the assemblies of the prior art. While a particular structure of tube has been shown in the drawings, it is to be understood that other conventional tubes may be utilized as well. Of primary importance is the adaptation of the cavity resonator portions comprising the filled dielectric to form an integral part of the tube wall structure and thereby to accommodate and support the various tube parts. In this way, the integrity and operation of the tube is not altered in any way while the benefits of the improved structure are readily ascertainable.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. High frequency apparatus comprising:

(a) a tube portion including a cathode, a grid, an

anode, and a surrounding wall structure therefor;

(b) a resonator portion including first and second members of solid dielectric material coated on the outside surface portions thereof with conductive material, said first and second members being selected portions of the wall structure of said tube portion and together with said conductive material forming first and second internal resonators partly filled by said dielectric material;

(c) means for electrically connecting said conducting surfaces of said first and second resonators; said electrical connecting means being insulated from said grid; and

(d) said anode being disposed within said first resonator and said cathode being disposed within said second resonator.

2. The device as recited in claim 1 wherein said solid dielectric material comprises a ceramic.

3. The device as recited in claim 1 wherein means are provided communicating with said first and second resonators for feeding back energy from said first resonator to said second resonator.

4. The device as recited in claim 1 wherein a contact ring is provided in the wall structure of said tube portion for electrically connecting said conducting film of said resonator portion with said cathode.

5. The device as recited in claim 1 wherein said tube wall structure includes capacitive means coupling said anode and said conducting film of said resonator portion.

6. The device as recited in claim 3 wherein said tube wall structure includes capacitive means coupling said grid and said conducting film of said resonator portion.

7. High frequency apparatus comprising:

(a) a tube portion including a cathode, a centrally apertured grid, an anode, and a surrounding wall structure therefor;

(b) a resonator portion including first and second members of solid dielectric material coated on the out side surface portions thereof with conductive material, said first and second members being selected portions of the wall structure of said tube portion and together with said conductive material forming first and second internal resonators partly filled by said dielectric material;

(0) means for electrically connecting said conducting surfaces of said first and second resonators, said electrical connecting means being insulated from said grid;

(d) said anode being disposed within said first resonator and said cathode being disposed within said second resonator; and

(e) energy feedback means providing communication with said first and second resonators for feeding back energy from said first resonator to said second resonator, said means comprising a probe member in electrical contact with said cathode and extending into the aperture of said grid for communicating with said first and second resonators.

8. High frequency apparatus comprising:

(a) a tube portion including a cathode, a grid, an anode, and a surrounding wall structure therefor; and

(b) a resonator portion comprising:

(1) a first resonator disposed about at least a portion of said anode including solid dielectric material of preselected volume for the desired resonating frequency coated on the outside surface portions thereof with conductive material, said dielectric material being integral with said surrounding wall structure of said tube portion,

(2) a second resonator disposed about at least a portion of said cathode including solid dielectric material of preselected volume for the desired resonating frequency coated on the outside surface portions thereof with conductive material, said dielectric material being integral with said surrounding wall structure of said tube portion,

(3) means for electrically connecting said conducting surfaces of said first and second resonators, said conducting surfaces being electrically insulated from said grid.

9. The device as recited in claim 8 wherein means are r provided communicating with said first and second resonators for feeding back energy from said first resonator to second resonator.

References Cited UNITED STATES PATENTS 2,351,895 6/1944 Allerding 315-39 3,025,477 3/1962 Swain 33110l X 3,054,012 9/1962 Schade 313-46 3,237,122 2/1966 Campi 33199 X 3,360,743 12/1967 Clark 331-98 HERMAN KARL SAALBACH, Primary Examiner S. CHATMON, In, Assistant Examiner U.S. Cl. X.R. 331-97 

